It is known in the mechanical arts to provide split bearing assemblies in various structural and machine components for supporting, or being supported by, the journals of rotating shafts and the like. Examples of applications for split bearing assemblies include engine crankshaft main and connecting rod bearing assemblies, some camshaft bearing assemblies, crank-supporting bearing assemblies for compressors, presses and other machines, and other rotatable shaft-supporting bearing assemblies, in all of which a removable saddle-like bearing cap is secured to a mating saddle-like main body to provide for the installation and removal of a rotatable shaft, an attached connecting rod, or another device.
Undoubtedly the most common method for manufacturing the separable main bodies and caps of split bearing assemblies is to separately form them by casting, forging or otherwise, whether they be for connecting rods, engine crankcases or other devices, and to subsequently bolt, or otherwise secure together, the caps and the main bodies. In many cases, finish machining of the journal encircling opening is completed after initial assembly of these components. This manufacturing method requires a large number of machining operations, as well as preliminary assembly and disassembly of the components, before the supporting or supported shaft may be installed.
Another known manufacturing method involves forming the main body and cap integral and separating them during manufacture by sawing or cutting away excess material provided to initially join the components. This method also requires machining of the connecting surfaces and other portions, generally including preliminary assembly.
In the case particularly of connecting rods, the prior art teaches other methods of forming the main body and cap as integral members and completely machining all necessary surfaces, including the journal encircling opening or bore, before separating the main body and cap members. The members are separated by material fracture techniques which involve fracturing the components along predetermined fracture planes, leaving interlocking rough surfaces that are capable of being re-engaged for assembly of the components into an operating assembly.
The prior art fracture techniques include various methods of weakening the separation planes, such as by drilling holes therein and/or providing weakening notches along one or more edges. Embrittlement of the material in the separating planes may also be provided for either by material selection, heat treatment (including hardening of various types), or by freezing the material to reduce its temperature below the embrittlement point.
The various types of prior fracture techniques introduce various problems, among which are reduction of the engageable surface area of the separated parts that reduces the allowable clamping load and, in some cases, the introduction of excessive bending of the separating parts which results in yielding deformation of metal along the edges that interfere with proper reassembly of the separated components. Deformation of the previously machined opening can also be a problem with some methods. Such difficulties limit the useable applications of fracture techniques and sometimes require additional machining operations to clean up or correct deformation and yielding problems.